4,946 research outputs found

    Measuring CMB Polarization with ESA PLANCK SubMM-Wave Telescope

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    We analyze the polarization properties of the tilted off-axis dual-reflector submillimeter-wave telescope on the ESA PLANCK Surveyor designed for measuring the temperature anisotropies and polarization characteristics of the cosmic microwave background.Comment: 5 pages, 4 figures, 1 tabl

    A variationally computed line list for hot NH3

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    We present 'BYTe', a comprehensive 'hot' line list for the ro-vibrational transitions of ammonia, 14NH3, in its ground electronic state. This line list has been computed variationally using the program suite TROVE, a new spectroscopically-determined potential energy surface and an ab initio dipole moment surface. BYTe, is designed to be used at all temperatures up to 1500K. It comprises 1137650964 transitions in the frequency range from 0 to 12000 cm-1, constructed from 1366519 energy levels below 18000 cm-1 having J values below 36. Comparisons with laboratory data confirm the accuracy of the line list which is suitable for modelling a variety of astrophysical problems including the atmospheres of extrasolar planets and brown dwarfs.Comment: the paper has been submitted to MNRA

    TOWARDS THE UNDERSTANDING BETWEEN ENVIRONMENTALISTS AND CORPORATIONS

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    The academic area is full of ideas that suggest solutions on how to cope with climate change yet, the world of technology, corporations with big financial turnover, are slow to implement their solutions. Perhaps, the ecological civilization, towards which we aim, has the other side to consider and the solution must be cumulative, not just theoretical or financial

    The Status of Spectroscopic Data for the Exoplanet Characterisation Missions

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    The status of laboratory spectroscopic data for exoplanet characterisation missions such as EChO is reviewed. For many molecules (eg H2O, CO, CO2, H3+, O2, O3) the data are already available. For the other species work is actively in progress constructing this data. Much of the is work is being undertaken by ExoMol project (www.exomol.com). This information will be used to construct and EChO-specific spectroscopic database.Comment: Experimental Astronomy, accepte

    ExoMol line lists IV: The rotation-vibration spectrum of methane up to 1500 K

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    A new hot line list is calculated for 12^{12}CH4_4 in its ground electronic state. This line list, called 10to10, contains 9.8 billion transitions and should be complete for temperatures up to 1500 K. It covers the wavelengths longer than 1 μ\mum and includes all transitions to upper states with energies below hc18000hc \cdot 18\,000 cm1^{-1} and rotational excitation up to J=39J=39. The line list is computed using the eigenvalues and eigenfunctions of CH4_4 obtained by variational solution of the Schr\"{o}dinger equation for the rotation-vibration motion of nuclei employing program TROVE. An ab initio dipole moment surface and a new 'spectroscopic' potential energy surface are used. Detailed comparisons with other available sources of methane transitions including HITRAN, experimental compilations and other theoretical line lists show that these sources lack transitions both higher temperatures and near infrared wavelengths. This line list is suitable for modelling atmospheres of cool stars and exoplanets. It is available from the CDS database as well as at www.exomol.com.Comment: Submitted to MNRA

    ExoMol: molecular line lists for exoplanet and other atmospheres

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    The discovery of extrasolar planets is one of the major scientific advances of the last two decades. Hundreds of planets have now been detected and astronomers are beginning to characterise their composition and physical characteristics. To do this requires a huge quantity of spectroscopic data most of which is not available from laboratory studies. The ExoMol project will offer a comprehensive solution to this problem by providing spectroscopic data on all the molecular transitions of importance in the atmospheres of exoplanets. These data will be widely applicable to other problems and will be used for studies on cool stars, brown dwarfs and circumstellar environments. This paper lays out the scientific foundations of this project and reviews previous work in this area. A mixture of first principles and empirically-tuned quantum mechanical methods will be used to compute comprehensive and very large rotation-vibration and rotation-vibration-electronic (rovibronic) line lists. Methodologies will be developed for treating larger molecules such as methane and nitric acid. ExoMol will rely on these developments and the use of state-of-the-art computing.Comment: MNRAS (in press

    The ExoMol Atlas of Molecular Opacities

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    The ExoMol project is dedicated to providing molecular line lists for exoplanet and other hot atmospheres. The ExoMol procedure uses a mixture of ab initio calculations and available laboratory data. The actual line lists are generated using variational nuclear motion calculations. These line lists form the input for opacity models for cool stars and brown dwarfs as well as for radiative transport models involving exoplanets. This paper is a collection of molecular opacities for 52 molecules (130 isotopologues) at two reference temperatures, 300 K and 2000 K, using line lists from the ExoMol database. So far, ExoMol line lists have been generated for about 30 key molecular species. Other line lists are taken from external sources or from our work predating the ExoMol project. An overview of the line lists generated by ExoMol thus far is presented and used to evaluate further molecular data needs. Other line lists are also considered. The requirement for completeness within a line list is emphasized and needs for further line lists discussed

    Detecting chirality in molecules by linearly polarized laser fields

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    A new scheme for enantiomer differentiation of chiral molecules using a pair of linearly polarized intense ultrashort laser pulses with skewed mutual polarization is presented. The technique relies on the fact that the off-diagonal anisotropic contributions to the electric polarizability tensor for two enantiomers have different signs. Exploiting this property, we are able to excite a coherent unidirectional rotation of two enantiomers with a {\pi} phase difference in the molecular electric dipole moment. The approach is robust and suitable for relatively high temperatures of molecular samples, making it applicable for selective chiral analysis of mixtures, and to chiral molecules with low barriers between enantiomers. As an illustration, we present nanosecond laser-driven dynamics of a tetratomic non-rigid chiral molecule with short-lived chirality. The ultrafast time scale of the proposed technique is well suited to study parity violation in molecular systems in short-lived chiral states
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